-LRB- CNN -RRB- -- The Rev. Billy Graham 's son is requesting prayers for his ailing father .

Franklin Graham said that his father , who turned 95 in November , is extremely weak , but his vitals are good .

`` Our family would appreciate your prayers for him that the Lord would strengthen him , '' the son wrote in a prayer request posted Tuesday on the website of the Billy Graham Evangelistic Association .

`` Only the Lord knows what is in store as we move forward in service to Him , '' he said .

The elder Graham returned home late last month , two days after he was admitted to a hospital for pulmonary-related tests and observation . He was admitted to the hospital in October for similar tests .

Graham , who lives in western North Carolina , has provided counsel to generations of U.S. presidents , beginning with Harry S. Truman .

Staging revivals that he called `` crusades '' around the world , the founder of the Billy Graham Evangelistic Association has reached untold millions of people in person .

Graham began his missionary work in 1944 when he started speaking at rallies for the Youth for Christ/Campus Life ministry . Five years later , he was holding a `` crusade '' in tents in downtown Los Angeles .

`` We value your prayers -- in fact , we depend on them , '' his son wrote in the request .

`` We find words of comfort and praise in the psalms , ` Oh , bless our God ... and make the voice of His praise to be heard , who keeps our soul among the living , and does not allow our feet to be moved . Come and hear , all you who fear God , and I will declare what He has done for my soul . Blessed be God , who has not turned away my prayer . ' ''

CNN 's Janet DiGiacomo and Phil Gast contributed to this report .

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The Rev. Billy Graham celebrated his 95th birthday in November

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He is extremely weak , but his vitals are good , his son says

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Graham was hospitalized last month for pulmonary-related tests and observation